1. Field of the Invention
This invention relates to paper/film composite structures which can be recycled for paper reuse without previously removing film portions.
2. Background Art
Nowadays, many companies, municipalities and community units make efforts to recover a number of waste paper items including old news papers, magazines and corrugated fiberboard. Recovered waste paper items are transported to a recycle plant where they are processed and recycled for reuse. However, problems arise in recycling paper/film composite structures including windowed envelopes, wrapping materials provided with film portions through which the commodity inside is seen, and laminated paper items (e.g., dishes and cups) having a film laminated for imparting water resistance. This is because film portions are not removed during the waste paper processing and thus left in recycled paper to deteriorate its quality. Even when a filter is provided in the recycling process for removing the film, the filter is frequently clogged, which substantially lowers the efficiency of the recycling process. Thus, the waste paper recycle process is inoperative unless film portions are previously removed.
In fact, it is very cumbersome for each household or company to manually remove only film portions from waste composite structure items and put out only paper portions for recovery. Under the circumstances, such composite structure items are discarded as combustible waste or landfill.
To remedy the incompatibility of paper/film composite structure items with the waste paper recycling process, JP-A 2001-253015 discloses the use of water-insoluble, alkali-soluble cellulose derivatives such as dicarboxylic acid esters of hydroxyalkyl alkyl celluloses and cellulose acetate phthalate to form films.
This method has the benefit that film portions are removed during alkali treatment in the waste paper recycling process because the film is alkali soluble, eliminating a need to previously remove film portions. However, the following problem must be solved before this method can be commercially practiced. Films made of alkali soluble cellulose derivatives can be damaged during their working, transporting and service stages because of their low mechanical strength. The problem might be solved by using an alkali-soluble cellulose derivative having a high degree of polymerization or by increasing the film thickness to enhance the film strength. These approaches, however, undesirably increase the cost of film and are thus commercially unacceptable.